[FFmpeg-trac] #6311(ffmpeg:new): Unclear warning when encoding h264 from decklink without specifying pixel format.

[FFmpeg]

#6311: Unclear warning when encoding h264 from decklink without specifying pixel
format.
--------------------------------+---------------------------------------
             Reporter:  viddy   |                     Type:  enhancement
               Status:  new     |                 Priority:  minor
            Component:  ffmpeg  |                  Version:  git-master
             Keywords:          |               Blocked By:
             Blocking:          |  Reproduced by developer:  0
Analyzed by developer:  0       |
--------------------------------+---------------------------------------
 Summary of the bug:
 How to reproduce:
 {{{
 % ffmpeg -f decklink -i 'DeckLink SDI 4K at 14' -v verbose -c:v libx264 -an
 -preset medium -pix_fmt yuv420p -x264opts keyint=100:vbv-maxrate=5500:vbv-
 bufsize=5000:bitrate=5000 -threads 16 -f mpegts -tune film

 ffmpeg version N-85469-gf1d80bc Copyright (c) 2000-2017 the FFmpeg
 developers
   built with gcc 4.9.2 (Debian 4.9.2-10)
   configuration: --enable-shared --enable-libx264 --disable-stripping
 --enable-gpl --enable-nonfree --enable-libvpx --enable-libvorbis --enable-
 libfdk-aac --enable-decklink --extra-cflags=-I/root/decklink-
 sdk/Linux/include --extra-ldflags=-L/root/decklink-sdk/Linux/include
 }}}

 This warning shows up:
 {{{
 No pixel format specified, yuv422p for H.264 encoding chosen.
 Use -pix_fmt yuv420p for compatibility with outdated media players.
 }}}

 A warning I read, and then disregarded since I wasn't considering my
 players outdated.
 But in my later tests both Safari on latest macOS, and Chrome on latest
 Android will not play this H264-stream when delivered as HLS.

 Setting the pixel format to yuv420p solves this, and the stream plays fine
 in Safari (macOS) and Chrome (Android) after this.

 Suggested solution
 1) Make the warning message clearer. Suggestion:
 {{{
 Use -pix_fmt yuv420p for compatibility with outdated media players and
 some embedded media players within browsers (e.g Chrome on Android and
 macOS Safari as HLS)
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6311>
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